The present invention relates to electrically actuated and particularly solenoid operated waterfill valves for appliances such as clothes washing machines, dishwashers and automatic ice makers for refrigerators. Appliances of this type, particularly those for household or domestic use, employ low power solenoids for operating the water fill valve in response to a control signal from a programmer/timer employed for controlling the service cycle of the appliance.
In designing and manufacturing such solenoid operated water fill valves for appliances, it has been common practice to wind the solenoid coil of several thousand turns of fine magnet wire on a bobbin and pressure encapsulate the coil in a mold with injection of thermoplastic material. This type of solenoid construction has proven to be costly and difficult to control in high volume mass production of appliance water valves. In particular, the pressure of the heated thermoplastic during the encapsulation often results in movement and breakage of the fine wire of the coil resulting in scrappage of the coil after encapsulation. Furthermore, the encapsulation of the coils in a mold is a batch process and is inherently limited in production rate and thus adds to the manufacturing costs of the valve.
Heretofore, solenoid operated appliance water valves for appliances requiring high water fill flow rates have utilized a pilot operator to permit differential pressure across a diaphragm to provide the necessary force to open the main valve. This type of valve requires only a small force from the solenoid to operate the pilot valve. Typically, solenoid actuated pilot operated appliance water valves employ a pilot valve seat and passage through the diaphragm in order to provide water flow from the pilot passage to create the pressure differential across the diaphragm required to open the main valve.
Pilot operated valves of this type have utilized a plurality of small spaced apertures in the diaphragm to provide the bleed flow necessary to resupply the pilot chamber for equalizing the pressure across the diaphragm to enable the main valve to close when the pilot valve is closed. The small spaced holes in the diaphragm for providing bleed flow to the pilot passage have been the source of problems in appliance water valves inasmuch as foreign particles in the water supply can plug the bleed holes and cause insufficient water flow to the pilot passage and failure of the valve to close. Furthermore, the molding or punching of a small bleed passages through the diaphragm has proved to be a costly and difficult process to control in the molding of the elastomeric diaphragm.
Thus, it has long been desired to find a way or means of eliminating the pilot chamber bleed holes from the elastomeric diaphragm in a solenoid actuated pilot operated appliance water valve. It has also been desired to provide a simple and cost effective way of insulating the solenoid coil in such a water valve without exposing the fine coil wire to excessive pressures during thermoplastic encapsulation.